The present invention relates generally to hydrostatic relief valves, and more particularly to hydrostatic relief valves having integral filtering systems for use with tubs or spas which are substantially implanted in the ground.
Tubs or spas which are placed substantially at ground level are usually supported in the ground by placing a layer of sand on the floor of the excavation, on top of which the spa will rest. Although such a procedure provides the necessary support for the spa, it also permits ground water to accumulate beneath the spa. Depending upon the drainage for the particular location, considerable amounts of ground water may accumulate and exert substantial pressures on the spa, which is usually constructed of fiberglass. If the spa is then drained, such as for repairs, a large pressure differential across the spa is created. This pressure differential can cause considerable damage to the spa, including rupturing the spa or its plumbing connections.
Although it has been known to include a check valve in the base of a swimming pool, no such device has been used with hot tubs or spas to relieve excessive pressure differentials which may exist under the above-stated conditions. Those devices which have been used with swimming pools are unsatisfactory for use with hot tubs and spas because they allow waste which has accumulated under the spa to contaminate the spa's interior. In addition, such devices frequently are rendered inoperative because the sand and other particulate matter which accumulates under the spa becomes lodged in the check valve and prevents it from reseating, thereby leaving the interior of the spa in fluid communication with the ground water underneath.